Different temperature measurements for Gas turbines are known. Typically these are based on thermo couples or resistance thermometers. However, due to the harsh environment in a gas turbine they need to be capsuled for use in the pressurized flow path and are therefore relatively slow to detect transient changes in temperatures. Further, the hot gas temperatures in gas turbines are often too high for the use of direct measurements.
Optical pyrometers have also been used as a way to take spot readings (primarily in combustion zones). Optical pyrometers have not been widely used as continuous measurement devices in gas turbines. They do not work well below about 900° C. and would not be useful for monitoring during start-up and at low load. Further, optical access is difficult to the pressurized part of the gas turbine flow path.
The concept of measuring temperature based on the propagation speed of acoustic waves has been known for a long time. However, engine noise has so far prevented the use such a concept.